Polyphenols such as flavonoids have been shown to have beneficial health effects. In particular, polyphenols can provide beneficial effects by lowering the side effects of co-administered therapeutic agents, in some cases acting as Tissue transport protein modulators. While blood tissue barrier structures, such as the blood-brain barrier (BBB, blood pancreas barrier, blood kidney barrier, and blood-placenta barrier), function as n obstacle to a isolate the tissues from the systemic blood circulation, some pharmaceutical agents, such as anesthetic agents, cross the tissues selectively causing tissue specific toxicity or side-effects rather than a desired localized action. In addition, blood tissue barriers may be compromised by disease states and therapeutic treatments, causing barrier laxity and then permitting unwanted agents to cross the barrier and adversely affect tissue structures. Thus, there is a continued need in the field for compounds that will lower side effects of co-administered therapeutic agents, such as new tissue transport protein modulators, and for compositions and methods for improved delivery of polyphenols, flavonoids, and related compounds.